1. Field of the Invention
The present invention relates to a ball grid array electronics assembly wherein individual solder balls of the assembly are electrically accessible for testing purposes, a method of assembling such a package, and a method of testing an electrical device which has hidden connections.
2. Discussion of Related Art
An electronics assembly often comprises a substrate and an electrical device such as an integrated circuit. An array of solder balls may be used to attach the electrical device to the substrate. The electrical device may be mounted in a manner that prevents access to the solder balls.
It may in certain instances be required to test the electrical device by making electrical contact with one or more of the solder balls individually. Since the solder balls are hidden behind the electrical device and only a small gap exists between the substrate and the electrical device such electrical testing may not be possible.
One technique for testing such an electrical device involves forming electrical traces on the substrate. The traces contact the solder balls and extend out from under the electrical device to an accessible location on the substrate. A probe connected to an electrical tester may then be used to contact the traces at the accessible location. The electrical tester may then be used to test the electrical device.
The formation of additional traces on a substrate, such as a printed circuit board, leads to a larger, more costly substrate. Additionally, the test traces occupy valuable board space and limit the input/output and/or require more substrate layers. What may therefore be required is a solution wherein individual solder balls in a ball grid array assembly can be accessed for testing purposes and wherein additional traces do not have to be made on a substrate such as on a printed circuit board.